1. Field
The present disclosure relates generally to communication, and more specifically to techniques for accessing and monitoring wireless communication systems.
2. Background
Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, video, broadcast, messaging, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources. Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal Frequency Division Multiplexing (OFDM), and Opportunity Driven Multiple Access (ODMA). A CDMA system may implement a radio access technology (RAT) such as Wideband-CDMA (W-CDMA) or cdma2000, which covers IS-2000, IS-856, and IS-95 standards. A TDMA system may implement a RAT such as Global System for Mobile Communications (GSM). These various RATs and standards are known in the art.
Some wireless communication systems are capable of providing voice and packet data services, which may be referred to as “data and voice” systems. One such system is a 1xEV-DV (“Evolution Data-Voice”) system that implements IS-2000 and/or IS-95. Voice and packet data services have different characteristics. For example, voice service typically requires a common grade of service (GoS) for all users as well as relatively stringent delays. In contrast, packet data service may be able to tolerate different GoS for different users and variable delays. To support both voice and packet data services, the 1xEV-DV system may first allocate system resources to voice users and then allocate any remaining system resources to packet data users who are able to tolerate longer delays.
Some wireless communication systems are optimized for packet data service, which may be referred to as “data only” systems. One such system is a 1xEV-DO (“Evolution Data-Optimized”) system that implements IS-856. Packet data transmission is typically characterized by long periods of silence punctuated by bursts of traffic.
A service provider may deploy multiple wireless communication systems to provide enhanced services for its subscribers. For example, the service provider may deploy a 1xEV-DV system to provide voice and packet data services for a large geographic area and may deploy a 1xEV-DO system to provide packet data service for areas where packet data usage is expected to be high. The coverage areas of the two systems typically overlap.
A hybrid terminal may be capable of communicating with the 1xEV-DV and 1xEV-DO systems. The terminal is typically able to receive service from one of the two systems at any given moment depending on the location of the terminal and the desired service. The terminal may have registered with the 1xEV-DV system and may be monitoring this system for page and other messages. The terminal may thereafter attempt to access the 1xEV-DO system to obtain packet data service. The terminal would then enter a 1xEV-DO access state and perform a sequence of tasks in order to access the 1xEV-DO system. During the time that the terminal is in the 1xEV-DO access state, the terminal is typically not able to monitor the 1xEV-DV system for page and other messages. Consequently, the terminal may miss an incoming call while attempting to access the 1xEV-DO system, which is highly undesirable.